Attribute Isolated Scope

Defined with an @ symbol
Binds a local scope property to the value of a DOM attribute The binding is uni-directional from parent to directive
The result is always a string because DOM attributes are strings

Binding Isolated Scope

Defined with an = symbol
Bi-directional binding between parent and directive You can define the binding as optional via =? Optimal for dealing with objects and collections

Expression Isolated Scope

Defined using an & symbol
Allows you to execute an expression on the parent scope To pass variables from child to parent expressions you must use an object map